I'm trying to build a 6 buttons stick using Emanuele Bettidi schematic. I remade it under Eagle (link).
Here's an image export is you don't have Eagle (link).
I'll try to make the circuit this week. But it promises to be painful as the original board has 2 layers (hires phoso)

I was at a bbq this week-end. I snatched a japanese hardware hacking book and took some photos with my cell phone
It's basically an article about how to make a 6 buttons arcade stick for the PC Engine.